1. Technical Field
The present invention relates to a color processing apparatus and a computer-readable medium storing a program that causes a computer to execute color processing.
2. Related Art
An output device outputs a color image using plural colors. In general, color components of a color signal received in the output device are different from colors used in the output of an image. Therefore, there is a need to convert the received color signal into a color signal having colors which are to be used as its components. As one example, the color signal received in the output device may include the L*a*b* color signal, a sRGB color signal, a sYCbCr color signal, etc. which are standardized device independent color signals. In addition to the basic colors, C (cyan), M (magenta), Y (yellow) or CMY and K (black) is used as colors in a color output device. Alternatively, in some cases, extra colors other than K may be additionally used.
As a method of converting a color signal received by an output device into a color signal having colors which are to be used as its components, for example, there is a method of using color conversion coefficients calculated by a physical model such as the Neugebauer equation. In addition, as methods of providing precise color matching, for example, there are methods described in JP Hei. 10-262157 A (which corresponds to U.S. Pat. No. 6,100,999) and JP 2002-84434 A, and a method of involving a correspondence relationship learning model using a neural network. That is, a color patch is generated corresponding to plural combinations for components of colors used by an output device, the color patch is output and colorimetrically measured, a correspondence relationship between the components of each color which is to be used and colorimetric values are modeled, and color conversion is performed using this model.
In addition, in recent years, in some cases, extra colors other than K have been used for improvement of granularity and enlargement of a color gamut. For example, there are cases of using six CMYKOG colors (O=orange, G=green) and seven CMYKRGB colors (R=red, G=green, B=blue). In these cases, a three-dimensional color signal received by an output device is converted into a six-dimensional or seven-dimensional color signal.